1. Field of the Invention
The present invention relates to a positional measurement system which measures a three-dimensional position of the source of electromagnetic waves, through use of a lens system and a mirror system which form an area where electromagnetic waves, such as light or radio waves, are concentrated, and a receiving device for detecting the concentrated area of electromagnetic waves.
2. Description of the Related Art
A conventionally known method for measuring a three-dimensional position of an illuminant (or an object having high luminance) is to compute coordinates of the illuminant according to the principle of triangulation which takes a distance between two digital cameras as a base line, by photographing the illuminant with the digital cameras. However, this method requires two or more cameras and involves problems of high costs and troublesome positional adjustment of optical axes of the respective cameras to the base length. Additional problems are the necessity for photographing an object after obtaining correct focus so as to prevent generation of an out-of-focus image of the object and the ability to perform, at most, ten photographing operations, or thereabouts, per second. Put another way, in the case of an object which moves at high speed, focusing fails to catch up with the motion of the object. This in turn results in a problem of a failure to measure a position or another problem of the object being out of focus, which drastically deteriorates positional accuracy or the power of resolution.
A light interference method is known as a method for measuring the position of an illuminant with high accuracy. However, this method requires a large number of components and high costs. Further, assembly of these components requires a high degree of positional accuracy, which presents a problem of high costs and consumption of efforts. Moreover, an automatic focusing mechanism is required, which has a drawback of inability to perform high-speed measurement or the like. Moreover, the laser beam is radiated on an object after having been formed in the shape of a spot or a line, and hence safety precautions must be taken.
As mentioned before, in order to measure the three-dimensional position of the illuminant with high accuracy and high resolution, the large number of components and high costs are required. In addition, consumption of much time for focusing is required, thus there is difficulty in increasing the speed of measurement. Moreover, under the light interference method, assembly requires high positional accuracy. Hence, the method has problems of high costs and requirement of taking safety precautions because of using laser. Another problem of the light interference method is complicated computation for measuring a position from the interference pattern.
A method for capturing a point of illumination with a special lens and a special sensor has already been provided. However, under this method, highly-accurate measurement of a position of a light source located several meters away requires a hemispherical lens having a large diameter. Thus, this method involves a problem of an increase in the weight of the lens and costs of materials. Specifically, under this method, a practical device encounters difficulty in highly-accurately measuring the position of the light source located several meters away.